Hong Kong's umbrella revolution 'is not dead'

Media reactions to Boris Nemtsov's murder

Deadly double bombing in Istanbul

Two bombs exploded in western Istanbul on Sunday, killing at least 17 and wounding over a hundred people. Though no-one has yet claimed responsibility, the city's governor says he is 'certain' it is a terror attack.

Turkish Prime Minister Recep Tayyip Erdogan on Monday joined thousands at the funerals of victims of two Istanbul bomb attacks which killed 17 people amid accusations they were planted by Kurdish separatists.

The attack Sunday night, in which more than 150 people were wounded, heightened tensions as the Constitutional Court met to decide whether Erdogan's ruling Islamist-rooted Justice and Development Party (AKP) should be banned on charges that it sought to undermine Turkey's secular system.

Erdogan did not name the Kurdistan Workers' Party (PKK) but called the two explosions "the cost" of an intensified crackdown against the outlawed rebels in Turkey and neighbouring northern Iraq.

"Unfortunately, the cost of this (military action) is heavy. The incident last night was one such example," Erdogan said at the scene of the blasts as residents chanted "Down with the PKK."

The PKK denied involvement, blaming "sinister forces".

But there was more condemnation of the group when Erdogan and other ministers joined thousands of people at the funerals of 10 of the victims at a local mosque.

The coffins and nearby buildings were covered in the national flag and the angry crowd shouted slogans against the PKK.

A senior Kurdish militant, Zubeyir Aydar, told the pro-PKK Firat news agency, "The Kurdish liberation movement is not involved in this attack."

He said the blasts were the work of "sinister forces" and timed to coincide with the AKP trial and a case against the shadowy Ergenekon nationalist group alleged to have organised attacks and plotted assassinations to spark a military coup against Erdogan's government.

Sunday's explosions were the deadliest attack against civilians in Turkey since 2003, when alleged Al-Qaeda suicide bombers killed 63 people in Istanbul.

Condemnation was sweeping worldwide.

UN chief Ban Ki-moon "strongly condemns yesterday’s bombings in Istanbul...(and) his sympathies to the families of the victims and the wounded," his spokeswoman Michele Montas said in a statement.

In Washington, National Security Council spokesman Gordon Johndroe said the US stands as a partner "with the people of Turkey as they confront terrorism," as Europe slammed the "heinous" attacks.

The bombs were planted in concrete rubbish containers on a crowded street lined with shops and cafes in the popular Gungoren neighbourhood on Istanbul's European side.

A small device created the initial panic, officials said. A second, more powerful explosion nearby followed about 10 minutes later as passers-by and residents milled around the site.

Istanbul Governor Muammer Guler said five of the 17 dead were children and warned that six people remained in critical condition.

All the dead came from the second blast, including a 12-year-old girl hit by shrapnel as she stood watching from a fourth-storey balcony, Anatolia news agency reported.

Asked whether the PKK was responsible, Guler said "a link is seen with the separatist organisation" and police are working on it, Anatolia reported.

Erdogan pledged that the perpetrators would be caught and punished.

"Those responsible for this savagery, wherever they are, will not escape the end that awaits them," he said. "The strongest response our nation will give to this attack... will be to strengthen our unity."

At about the same time as the Istanbul attack, a Kurdish militant hurled a hand grenade at a police station in Bingol, in Turkey's mainly Kurdish southeast, before being shot dead, officials said.

Two other militants who took part in the attack were wounded and captured.

The PKK, listed as a terrorist group by Turkey and much of the international community, took up arms for Kurdish self-rule in the southeast in 1984, sparking a conflict that has claimed more than 37,000 lives.

Islamist and leftist groups have also struck in Istanbul, Turkey's biggest city.